In this paper some recent experiences in dam grouting in several countries are discussed where bentonite or Intraplast additives were used to control sedimentation, viscosity, grout density, set time, and strength. Also presented are recently developed theoretical and laboratory studies regarding the viscosity of grout slurries which point out the role of cohesion (yield point) of the grout in determining the penetration and uplift pressure exerted by the injected slurry. Results would appear to favor thicker, stable mixes.